Add valueOrDefault()

Author: tomphp

CHANGELOG.md

@@ -4,6 +4,10 @@ This project adheres to [Semantic Versioning](http://semver.org/).<Paste>
 
 ## [Unreleased]
 
+## [0.2.4] - 2015-03-27
+### Added
+- `valueOrDefault()`
+
 ## [0.2.3] - 2016-03-22
 ### Added
 - `concat()`

README.md

@@ -257,3 +257,28 @@ function ($value) {
     return new Widget('first', $value, 'last');
 }
 ```
+
+#### T\valueOrDefault(mixed $default, callable $predicate = null)
+
+```php
+T\valueOrDefault('default')
+
+// Is equivalent to:
+
+function ($value) {
+    return $value ?: 'default';
+}
+```
+
+A predicate function can also be supplied:
+
+```php
+T\valueOrDefault('negative number', function ($value) {
+    return $value >= 0;
+})
+
+// Is equivalent to:
+
+function ($value) {
+    return $value >= 0 ? $value : 'negative number';
+}

src/transform.php

@@ -272,6 +272,27 @@ function newInstance($className, array $arguments = [__])
     };
 }
 
+/**
+ * Returns a transformer which returns the value, or a default value if the
+ * predicate fails when applied on the value. If no predicate is supplied then
+ * a null check is performed.
+ *
+ * @param mixed    $default
+ * @param callable $predicate
+ *
+ * @return \Clojure
+ */
+function valueOrDefault($default, callable $predicate = null)
+{
+    return function ($value) use ($default, $predicate) {
+        if ($predicate === null) {
+            return $value !== null ? $value : $default;
+        }
+
+        return $predicate($value) ? $value : $default;
+    };
+}
+
 /**
  * @internal
  *

tests/ValueOrDefaultTest.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace tests\TomPHP\Transform;
+
+use PHPUnit_Framework_TestCase;
+use TomPHP\Transform as T;
+
+final class ValueOrDefaultTest extends PHPUnit_Framework_TestCase
+{
+    /** @test */
+    public function it_returns_value_if_it_is_not_null_and_no_predicate_is_supplied()
+    {
+        $fn = T\valueOrDefault('default');
+
+        $this->assertSame('value', $fn('value'));
+    }
+
+    /** @test */
+    public function it_returns_default_if_value_is_null_and_no_predicate_is_supplied()
+    {
+        $fn = T\valueOrDefault('default');
+
+        $this->assertSame('default', $fn(null));
+    }
+
+    /** @test */
+    public function it_returns_default_if_a_predicate_is_supplied_and_it_returns_false()
+    {
+        $predicate = function ($value) {
+            return $value === 'success';
+        };
+
+        $fn = T\valueOrDefault('default', $predicate);
+
+        $this->assertSame('default', $fn('fail'));
+    }
+
+    /** @test */
+    public function it_returns_value_if_a_predicate_is_supplied_and_it_returns_true()
+    {
+        $predicate = function ($value) {
+            return $value === 'success';
+        };
+
+        $fn = T\valueOrDefault('default', $predicate);
+
+        $this->assertSame('success', $fn('success'));
+    }
+}